Those who suffer from diabetes must control the level of blood sugar in their bloodstream on a daily, and sometimes hourly, basis. Insulin is only effective when injected directly into the bloodstream where it may be used by the body to counter/neutralize the effects of excessive blood sugar accumulation. Those who suffer from diabetes and their caregivers must become adept at determining the diabetic's blood sugar, calculating the correct dosage of insulin required to help return the blood sugar level to a normal range, loading a syringe with the calculated dosage, and administering the calculated dose through the use of the loaded syringe.
A standard syringe, as commonly available, consists of a hollow needle attached to the body of the syringe, also called the syringe barrel. The syringe barrel is a cylinder, into which a plunger is inserted, and that has a diameter calibrated such that a particular length of the barrel corresponds to a measured volume. The calibration volume is indicated by markings on the exterior surface of the syringe barrel. The user loads a syringe by placing the plunger at full depth in the syringe barrel such that the inserted end of the plunger is in contact with the base of the syringe barrel where the needle is attached to the barrel. The hollow needle is inserted into the compound, typically in liquid form, and the plunger is then pulled away from the end of the syringe barrel. When the plunger is pulled outward a gasket surrounding the plunger that is in contact with the interior wall of the syringe barrel is sufficient to cause a partial vacuum of sufficient strength to draw the compound into the syringe barrel via the hollow needle. The user watches the markings on the side of the barrel until the desired amount of the compound is drawn into the syringe. The user may then insert the hollow needle into an appropriate place on the body of the user, or another whom the user is assisting, and reverse the motion of the plunger to eject the compound from the syringe barrel into the body of the person who requires the compound. In the case of a diabetic the compound may be insulin.
A concern in the use of a standard syringe is that markings on the syringe barrel may be difficult to discern for a person who has diminished eyesight, for example, due to the detrimental effects to eyesight some diabetics experience. An additional concern is that the user may be unfamiliar with the dosage calculations, or may be uncertain as to how to know when the required dosage has been drawn into the syringe barrel and, as a result, draw too much or too little of the compound into the syringe barrel. A final concern is that the user, whether it is the diabetic or a caregiver, may be distracted and draw an inaccurate amount of the compound into the syringe barrel through simple inattention.